We are studying alterations of the cell surface of mouse and rat fibroblastoid cell lines which accompany cell transformation by SV40 virus. In particular, the increased synthesis and secretion of cellular plasminogen activator is being studied, to determine whether this change associated with viral transformation causes any of the cell surface changes characteristic of virus transformed cells. We also plan to examine whether the changes in synthesis and secretion of plasminogen activator, loss of a high-molecular-weight cell surface glycoprotein ("LETS" glycoprotein) and decreased cell-associated sulfated mucopolysaccharide synthesis, previously shown to be characteristic of SV40 transformed cells, are controlled by the expression of the SV40 A cistron in cells transformed by A cistron mutants of SV40. In addition, we are characterizing changes in the cell surface properties and decreased migration from capillary tubes of guinea pig peritoneal exudate cells (70% macrophage) exposed to culture fluids from SV40 transformed cells. BIBLIOGRAPHIC REFERENCES: Roblin, R., Chou, I.N., and Black, P.H. (1975) "Role of fibrinolysin T activity in properties of 3T3 an SV3T3 cells" In: Proteases and Biological Control, E. Reich, D. Rifkin and Shaw, Eds., Cold Spring Harbor Laboratory, pp. 869-884. Black, P.H., Chou, I.N., and Roblin, R. (1975). Differences in surface membrane components between normal, viral transformed and revertant cells. Proceedings of the XIth International Cancer Congress, Florence, 1974, Excerpta Medica International Congress Series No. 349, Vol 1, pp.119-129.